1. Field of the Invention
The invention relates generally to typewriters and, in particular, to apparatus for providing visual feedback to an operator regarding typewriter conditions or selections.
2. Statement Regarding the Prior Art
It is well known in the typewriter art to provide tab stop capability to facilitate the formatting of typewritten material. The tab stops are typically set by the operator in sequence and are stored either within a "mechanical memory", e.g., by displacing tab stop elements to an operative position, or within an electronic memory. Since the tab selection involves appearance considerations, it is desirable for the operator to have visual feedback of the stored tab settings.
In this regard, U.S. Pat. No. 3,923,138 describes a typewriter that provides visible feedback of a tab layout by means of indicator portions of selectively displaceable tab stop elements. Such indicator portions are displayed alongside a viewable scale which has markings corresponding to escapement distances.
Similarly, displaced elements are described for indicating margin selections and present carrier position in the IBM Technical Disclosure Bulletin dated 5/68, Vol. 10, No. 12 at page 1909. Unfortunately, "displaceable element" arrangements for indicating escapement positions are difficult to implement where position information is stored in an electronic memory and, in particular, where a plurality of selections are recallable at operator option.
Viewable feedback regarding escapement position settings that does not utilize mechanical displacement of indicator elements has been provided in typewriter systems employing video displays. For example, in U.S. Pat. No. 3,648,271, a video display is described that shows a scale corresponding to an operative pitch selection and indicates right and left margin positions on that scale. While such a video display offers great flexibility for operator feedback it is limited to rather expensive machines since the display and associated drive apparatus would typically have a cost that is substantial in relation to the cost of a basic typewriter.
It would be desirable to provide visual feedback of formatting selections in a low-priced typewriter. And, it would be desirable if the layout of a set of tabs selected from an electronic memory of a typewriter could be displayed to the operator so that selections among plural stored tab sets are conveniently reviewable.